With growing interest in energy saving and environmental issues in recent days as a backdrop, much attention has been paid to a hybrid vehicle. The hybrid vehicle has already been put into practical use and commercially available.
The hybrid vehicle is a vehicle having a DC (direct current) power supply, an inverter, and a motor driven by the inverter as a power source, in addition to an engine serving as a conventional internal combustion engine. That is, the hybrid vehicle obtains the mechanical power source not only by driving the engine but also by converting a DC voltage from a DC power supply to an AC voltage using an inverter, so as to rotate the motor with the resultant AC voltage.
Japanese Patent Laying-Open No. 2002-374604 discloses an example of a configuration of such a hybrid vehicle. According to this configuration, the hybrid vehicle includes a motor-generator for power generation and a motor-generator for driving. The motor-generator for power generation generates electric power using a portion of mechanical power generated from the engine, and the generated electric power is in turn used in the motor-generator for driving. Wheels receive the mechanical power from the engine and the motor-generator for driving, and rotate.
In the hybrid vehicle, there is a need to utilize the power generated by the on-vehicle motor-generator for power generation as commercial power supply. That is, the hybrid vehicle is utilized as the commercial power supply when commercial power supply facilities are not available in the vicinity such as in camping or when power failure occurs.
On the other hand, there is also a need to supply the hybrid vehicle with electric power from an external commercial power supply. That is, though electric power can be generated by the generator using the mechanical power from the engine, a battery serving as a DC power supply is charged by the external commercial power supply so as to allow use of an electrical appliance in the vehicle without operating the engine.
Japanese Patent Laying-Open Nos. 2002-374604 and 2000-278808 disclose a vehicle including a socket outlet for AC 100V. In addition, documents in the following also show the background art: Japanese Patent National Publication No. 2002-534050; and Patrick W. Wheeler et al., “Matrix Converters: A Technology Review”, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, April, 2002, Vol. 49, No. 2, pp. 276-288.
FIG. 9 illustrates energy transmission in a conventional hybrid vehicle.
Referring to FIG. 9, the conventional hybrid vehicle includes an engine 502, a motor-generator MG1, an inverter 537 connected to motor-generator MG1, a motor-generator MG2, and an inverter 536 connected to motor-generator MG2.
The hybrid vehicle further includes a battery 512, a capacitor C501 stabilizing a voltage applied to opposing ends of the battery, a planetary gear 516 connected to engine 502 and motor-generators MG1, MG2, and a tire 520 driven by planetary gear 516.
Planetary gear 516 is connected to motor-generators MG1, MG2 and engine 502, and serves as a power split device dividing the mechanical power among these three components.
As shown in FIG. 9, in a normal running state, though energy generated from rotation of engine 502 is partially transmitted for driving the tire as shown with an arrow P3, the energy is mostly used for rotating motor-generator MG1 as shown with an arrow P1 so as to generate power.
Three-phase AC power generated by motor-generator MG1 is once converted to DC power by inverter 537. The DC power output from inverter 537 is stored in battery 512 or capacitor C501. Meanwhile, inverter 536 receives the DC power from battery 512 and capacitor C501 and drives motor-generator MG2. The rotation energy from motor-generator MG2 drives tire 520 as shown with an arrow P2.
In other words, in the conventional hybrid vehicle, most energy is transmitted from the engine to motor-generator MG1. Then, the generated power is converted from AC to DC and converted again from DC to AC by inverter 536, and finally converted to mechanical power in motor-generator MG2.
In this manner, a path to transmit the power from motor-generator MG1 through inverters 537, 536 to motor-generator MG2 passes through the inverter twice, which results in poor power conversion efficiency. In addition, when the power generated by motor-generator MG1 is converted to DC by inverter 537, the power is once stored in battery 512 or capacitor C501, in which case, life of the battery and need for a relatively large capacitor are matters of concern.
Moreover, Japanese Patent Laying-Open No. 2002-374604 provides an additional power converter dedicated for AC 100V in order to output AC 100V from the vehicle. That is, there is a disadvantage that the dedicated power converter should additionally be provided in order to output the commercial power supply of AC 100V from the hybrid vehicle.